Combustion zone control



NOV. 28, 1944. H KRElslNGER TAL 2,363,875

COMBUSTION ZONE CONTROL 3 Sheets-Sheet l Filed Nov. 25, 1941 fof NOV-28, 1944. H. KRElslNGER r-:TAL 2,363,875

COMBUSTION ZONE CONTRL Filed NOV. 25. 1941 5 Sheets-Sheet 2 IN V ENT 0K5HTTORNEY Nov'. 28, 1944. H. KREISINGER r-:T AL 2363875 COMBUSTION ZONECONTROL'V 'Filed Nov. 25, 1941 v 5 Sheets-Sheet 3 lNlfEq/ToRs @myKrezsngge WI/4r mms Z. faraffh v mmm/EY Patented Nov..-28, 1944 UNITEDSTATES PATENT oEFlcE COMBUSTION ZONE CONTROL Henry Kreisinger, Piemont,and Virginlus Z. aracristi, Bronxville, N. Y., asslgnors to CombustionEngineering Company, Inc., New York,

Application November 25. 1941. Serial No. 420,356

2 Claims.

This invention relates to an improvement in the regulation of thetemperature of steam leavingv a superheater. It is particularlyapplicable to a superheater so located in a boiler that substantiallyallof the heating effect is by convection from the products of combustionfrom a furnace whose walls are lined with water cooled surfaces and inwhich turbulent ring is employed.

It is well known that in the operation of such a steam generating unitthe temperature of the superheated steam varies with fluctuations insteam output, a reduction in superheat occurring with a reduction inrating. Because this is undesirable various means have been devised tocorrect for steam temperature variations.

One method. of regulating the temperature of superheated steam is tocause a variation in the heat absorption within the furnace from thefuel burnt therein so that the gases passed over the superheater surfaceare at a temperature capable of producing the desired degree ofsuperheat. A method of this nature is dis closed in the patent toKruger, No. 2,243,909, of June 3, 1941. It has been found, however, thatKrugers method is inadequate to meet the large variations of superheatcontrol now required in boilers of great steam generating capacity and,accordingly, it is an object of this invention to provide an improvedmethod of regulating'the heat absorption within the furnace so as toobtain the desired steam temperature from the superheater.

How the foregoing together with other objects and advantages as mayhereinafter appear or are incident to our invention are realized isillustrated in preferred form in the accompanying drawings wherein:

Figure 1 is a sectional elevation of a steam generating unit embodyingthe invention;

Figure 2 is a sectional elevation showing a modifled form for the lowerpart of the furnace of Fig. 1;

Figure3 is an enlarged vertical sectional View through a typical set offuel burners shown in Fig. 1; I l

Figure 4 is a horizontal schematic view, taken through the furnace onthe line 4-4 in Fig. l; and

Figure 5 is a vertical sectional view of a modifled form for the burnersshown in Fig. 3.

In Figure l the boiler illustrated includes a lower water drum I0 andupper steam and water drum II interconnected by steam generating tubesI2. A superheater I3 receiving the saturated steam generated is locatedin the llrst pass of the boiler and balilesA I4 and I5 cause the gasesfrom the ofltake of furnace I6 to pass serially over superheater I3, atube bank I I and on to the boiler offtake.

In Figure 1 the furnace IB has its walls lined with water cooled tubes20. The bottom of the furnace is suitably constructed to 'retain slag ina fluid condition, the slag overflowing through an opening 2l. Near thebottom of the furnace burners 22 are arranged preferably at the cornersas illustrated in Fig. 4.

In Figure 2 the lower part of the furnace BBA has two opposed sidessloping toward a throat 23 and Afaced with water cooled tubes fil. Thetwo remaining side walls also are lined with water cooled' tubesextending downwardly to the throat 23. 'I'he bottom and side walls abovethe throat thus form a water cooled hopper into which ash particles,gravitating from the fuel burning within the furnace, fall and, whilefalling, cool to a state in which they will not adhere to the sides ofthe hopper. The burners 22 in Fig. 2 are arranged somewhat above thehop- 25 per bottom and, as in Fig. 4, preferably at the corners.

Figure 4 shows the burners 22 arranged at the corners of the furnaceprojecting their streams of fuel and air into the furnace in directionstangential to the surface of an imaginary cylin-l der "C locatedvertically in the furnace, preferably in its center. Each set of burnersin Fig. 1 discharges three fuel streams into the furnace while each setof burners in Fig. 2 disl end of section 32. The tip 34 and section 33are formed at their juncture into a cylinder and sockl et joint. Thenozzle tip 34 is rectangular and located within and connected to atubular air deflecting vane 36, the whole, when turned up. wardlv ordownwardly directing the fuel and air stream accordingly. The tip 34 andvane are rotated by means of a. rod 31 connected at one end to the tipby an arm 40 fixed to a. pin 4I.

At its other end rod l1 carries apin 4I located in the slot 44 of a cam45. The cam 45 is mounted by a in 46 on a vertically movable bar 41 soit may ro te. An adjusting screw 48 which holds cam 45 at a. suitableangle with respect to bar 41 is fixed in its longitudinal movement bypivot block'll hinged. to the bar 41 by pin 50a. The screw 48 may beadjusted to draw the lower end of cam 45 closer to, or push it awayfrombar 41, thereby changing the angularity of the cam with respect tothe fbar. 'I'he bar 41 is limited to vertlcal movement by bearings El. Achange in angularlty of the cam 45 changes the movement of relatedconnecting rod 31 and the fuel nozzle tip 34 connected thereto. As shownin the drawings, the pin 43 is in mid-position in slot 44 and theconnecting rod 31 holds the tip 34 in position for horizontal dischargeof the fuel and air. When the bar 41 is moved down, carrying cam 45 withit. the tip 34 directs the fuel and air stream upwardly. Conversely anupward movement of bar 41 directs the fuel and air stream downwardly.The ba:- 41 may be moved to adjust the nozzle tip by a motor controlledfrom the switchboard for firing control.

Above and below each fuel nozzle 3l there are pivoted air deilectors 60that may be turned to direct the air horizontally, upwardly or down.-wardly. As shown, deectors are interconnected in pairs and operatingrods Bl are provided, the construction, operation and adjustments forthe respective deectors being the same as that dei scribed above forrotating the nozzle tips 34.

' Figure 5 shows a modified form of the end section for the nozzle. Thenozzle end section SIA itself is formed to direct the fuel and airstream upwardly at half of the maximum angle through which the tip 34Amoves from the horizontal. For example, if the tip 34A is movablethrough 45 deg., the inner end of section 3lA is turned upwardly 22%deg. This construction permits a greater vertical angle of discharge forthe fuel and air stream and yet provides a relatively smooth flowthrough the fuel nozzle for all angles.

The construction shown in Figure 5 may advantageously be used in aslagging bottom furnace such as shown in Figure 1. In this adaptationthree fuel burners are shown, the upper two of which may be madeadjustable upwardly to an angle of 45 deg. while the bottom one may be.adjustable 22l/2 deg. from the horizontal both.

upwardly and downwardly as provided for in Figure 3.

It is contemplated that the fuel nozzles may in addition be adjustablehorizontally as is shown in the patent to Kruger mentioned above.

In operation when all of the burners are adjusted to project the fueland air stream in a "l` substantially horizontal direction tangent tothe imaginary vertical cylinder C located centrally of the furnace, theburning fuel streams issuing from the four sets of corner locatedburners impinge upon one another resulting in a turbulent, rotatingmixture with a consequent rapid rate of combustion. This rapidcombustion produces a very high temperature in a zone A at the level ofthe burners near the bottom of the furnace so that there is a high rateof heat transfer from the flames to the water cooled wall tubes 20 inthis zone both by radiation and by convection. Leaving this zone the hotproducts of combustion pass 4upwardly and continue giving off heat tothe water cooled walls thereabove and exit from the furnace at arelatively low' temperature. When all of the burners are directedupwardly ascas'ns the streams of fuel are still tangent to an imagmaryvertical cylinder in the furnace but the lmpingement of ne burning fuelstreams upon one another is much less than when the burners arehorizontally directed as above described. This results in but relativelylittle mixing and turbulence and consequent slower or delayedcombustion. This delayed combustion occurs in a zone B, that is locatedhigher in the furnace than the zone A, and extends well into the upperpart of the furnace.' Consequently the temperature 'of the products ofcombustion leaving the furnace is relatively high because of the shorterpath through which they pass from the combustion zone to the outlet ofthe furnace and because tbe heat transfer from the flames to the watercooled walls at the bottom of the furnace is substantially less thanwith horizontally directed streams. The change in the direction of thefuel streams from the horizontal to an upward inclination results in a.rise in the temperature of the gases leaving the furnace which has beenfound adequate to change the rate of heat absorption by the superheaterI3 so that the steam temperature may be raised to that required forsatisfactory operation over a. greater range of ratings of the steamgenerating unit than heretofore attainable.

This invention in effect reduces the size of the furnace at the lowerratings of the steam generating unit, where lthe temperature of thesuperheated steam is relatively low. For example, at half rating abouthalf of the maximum amount of fuel that may be burned in the furnace isdelivered to the furnace near the bottom and burned there in zone A; theproducts of combustionlikewise are about half and dwell within thefurnace and are exposed to the cooled walls about twice as long as atfull rating. The exit temperature of the gases may then be too low forsuperheating the steam to the temperature desired. By raising the zoneof combustion within the furnace and delaying combustion by decreasingturbulence, the dwell of the products of combustion within the furnaceis reduced as is the area. of cooled furnace walls exposed to the gases.

In Figure 2 the burners are located higher than in Figure l and the zoneof most intense combustion may be moved below zone A to zone D, therebyincreasing the range through which said zone of combustion may be movedvertically in the furnace. y

According to the invention. not all of the burners need be adjusted to avertical angle; for example, the two upper burners 22 of each set may beso adjusted while the lower burner may be horizontal.

Any or all of the burners may also be made to be both vertically andhorizontally adjustable. When the furnace is operated with a layer of'molten lfluid slag on the furnace floor, it may bs advantageous tomaintain the bottom burners in position to direct the flame streamshorizontally or even downwardly over the slag so as to maintain it in ahuid condition throughout the lower furnace' while the upper burners areused to control the superheated steam temperaof the furnace from aplurality of points remote from the furnace outlet in such directions asto create a turbulent gas mass burning in a zone in the lower part ofthe furnace to transmit heat to the water tubes therein; maintaining,for a given load, a substantially uniform rate of fuel firing; andaltering the angle to the horizontal of the direction of the streams offuel and air so as to lower or raise the vertical location of thecombustion zone along the furnace axis as the. superheated steamtemperature respectively increases or decreases to thereby alter thelength of the path of gas travel through the furnace and the extent towhich gases are cooled before reaching the superheater.

2. The method of regulating the temperature of steam derived from asuperheater receiving its heat mainly by convection from gases flowingfrom the outlet at the upper part of a vertical furnace whose walls arelined with water circulating tubes comprising; introducing fuel and airinto the furnace from a multiplicity of points near the bottom of thefurnace and in directions substantially tangential to an imaginaryvertical n cylinder located centrally in the furnace for creating aturbulent rotating gas mass in\a zone 1ocated in the lower portion ofthe furnace to transmit heat to the water tubes therein; maintaining,for a given load, a substantially uniform rate of fuel lring; and, asthe supherheated steam temperature increases, decreasing the verticalangle of the directions of fuel introduction relatively to the furnacewalls to thereby increase the extent to which gases are cooled beforereaching the superheater.

HENRY KREISINGER.

VIRGINIUS Z. CARACRISTI. l

